<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1{
            width: 200px;
            height: 100px;
            background-color: crimson;
            position: absolute;
            z-index: 0;

        }
        #d2{
            width: 100px;
            height: 200px;
            background-color: limegreen;
            position: absolute;
            z-index: 1;

        }
    </style>
</head>
<body>
<div id="d1">

</div>
<div id="d2">

</div>
</body>
</html>